1. Field of the Disclosure
The present application relates to an offshore wind turbine, and particularly to a motion suppression device for a floating offshore wind turbine configured to suppress the swinging motion of the offshore wind turbine around a vertical axis, and a floating foundation for the offshore wind turbine having the motion suppression device for the offshore wind turbine.
2. Discussion of the Background Art
An offshore wind turbine generally employs a gravity foundation, a monopile foundation, a jacket foundation, a tripod foundation, a suction caisson foundation, or a floating foundation according to a depth of seawater and seabed geological conditions. Among all these foundation types, the floating foundation is not restricted by the seabed conditions and is applicable to an offshore wind farm having a water depth greater than 50 meters, thus the floating foundation is a promising technique which has a bright prospect for wide application.
Floating platforms in the marine industry and the offshore oil industry are similar to the floating foundation for the offshore wind turbine.
At present, an anti-roll device in the marine industry mainly includes a fin stabilizer, a bilge keel, an anti-roll tank, an anti-roll rudder, and so on, and the fin stabilizer, the bilge keel, and the anti-roll rudder may keep the ship stable by using the lift force of fluid acting on these structures during the navigation. The faster the ship travels the more stable the ship is. The anti-roll tank may keep the ship stable by using a pressure difference between ballast water in side tanks of larboard and starboard to offset an overturning moment of the ship.
A motion suppression device for the floating platform of the offshore oil projects mainly includes a damping plate for truss-spar and a stabilizing plate for floating bodies such as an FPSO.
However, the foundation for the floating offshore wind turbine bears loads quite different from the floating platforms in the traditional marine industry and offshore oil industry. In addition to combined loads from wind and wave, the foundation for the floating offshore wind turbine is also subject to a gyro revolving effect resulting from the operation of the wind turbine of a high-rise structure. The gyro revolving effect may generate overturning moments Mx and My and a torque Mz about a vertical axis on the foundation, and cause violent motions of the whole wind turbine in six degrees of freedom, including axial motions along axes X, Y, and Z and swinging motions about these axes, which may bring a tremendous challenge for a pitch and yaw control system of the wind turbine, and adversely affect the normal operation of the wind turbine, reduce the generated energy, or even endanger the structural safety of the whole system.
The foundation for the floating wind turbine is structurally different from the floating platform in the marine industry, and the loads, produced in the operation of machines carried on the foundation for the floating wind turbine is also different from that of the floating platform in the marine industry. At present, there is no effective motion suppression device specifically designed for overall motion of the floating offshore wind turbine. Therefore, it is necessary to provide a device for suppressing the motion of the floating wind turbine in six degrees of freedom.